Hi Gary,
Did your tech check R26 to see if it is shorted or open? I ask because I've seen this exact problem on three or four Mac Pluses and Pina's recommendation to check the corresponding resistor on the Plus always solved it.
My only uncertainty is that "The Dead Mac Scrolls" is pretty old and in a later book "Mac Classic and SE Repair and Upgrade Secrets" he writes that there were as many as five versions of the SE & SE/30 analog board, so I don't know if they all used R26 (as stated in Dead Mac Scrolls) for the focus circuit. Unfortunately, he doesn't mention focus problems at all in "Mac Classic and SE Repair and Upgrade Secrets" but he is very definite about it in the SE (same analog circuitry as SE/30) in "The Dead Mac Scrolls".
Jeff Walther
Did your tech check R26 to see if it is shorted or open? I ask because I've seen this exact problem on three or four Mac Pluses and Pina's recommendation to check the corresponding resistor on the Plus always solved it.
My only uncertainty is that "The Dead Mac Scrolls" is pretty old and in a later book "Mac Classic and SE Repair and Upgrade Secrets" he writes that there were as many as five versions of the SE & SE/30 analog board, so I don't know if they all used R26 (as stated in Dead Mac Scrolls) for the focus circuit. Unfortunately, he doesn't mention focus problems at all in "Mac Classic and SE Repair and Upgrade Secrets" but he is very definite about it in the SE (same analog circuitry as SE/30) in "The Dead Mac Scrolls".
Jeff Walther